Z-Score from Percentile Calculator

About this calculator

This calculator inverts the standard normal cumulative distribution function — computing the probit function, Φ⁻¹(p) — to find the z-score below which a given percentage of a normal distribution falls. Enter the 85th percentile, for example, and it returns z ≈ 1.04, meaning a value 1.04 standard deviations above the mean.

Statistics students use it to check inverse-normal problems without a z-table, test-score analysts use it to convert a percentile rank on a standardized test into a z-score for further statistical work, and Six Sigma and quality engineers use the same inverse-normal lookup when setting control limits or interpreting process capability against percentile targets.